Technical Field of the Invention
This invention relates generally to molded products and more particularly to a full graphics in-mold labels.
Description of Related Art
In-mold labeling involves the application of decorative labels during the molding process of plastic products. Combining the decoration and manufacturing of plastic products provides greater label durability compared to that of a post mold label when done properly. For proper adhesion, the in-mold label, which includes a substrate, ink, and sometimes a coating, must contain similar properties to that of the plastic product. For example, plastic cups are typically produced using polypropylene (PP), polyethylene (PE), polystyrene (PS), and polycarbonate (PC) and, accordingly, the in-mold label should have similar properties. As a specific example, stadium cups are currently fabricated using PP, but have very limited labeling options.
Styrene acrylonitrile, or SANS, is a styrene acrylic blend that produces a more durable plastic cup. Currently, however, SANS cups have not been commercially decorated other than via post molding decorating using silk screening, heat transfer, or hot stamping. There are several issues associated with the in-mold labeling process for plastic products including PP and SANS cups. For example, a mismatch in the properties of the ink, substrate, coating, or plastic product or improper molding techniques can cause label deformation, ink blow out (e.g., breakdown of ink, discoloration, and/or ink brittleness), blowing through the label, movement of the label, knit lines, label separation, and/or print distortion. As another example, if the ink has a different temperature range than that of the product, substrate, or coating, ink blow out can occur. As yet another example, movement or miss-registration of the label can occur when resin flows at a non-ideal rate during molding. As a further example, knit lines can occur where two flows come together within the label. As a still further example, label separation and/or print distortion can occur when the resin contains a different shrink and/or expansion rate than those of the substrates, inks, and/or coatings of the label. Another issue is cutting the in-mold labels, which can create debris from printing powder, ink, and/or “hairs”. These remnants need to be removed from the parts or will adversely affect the quality and appearance of the in-mold label and overall product.